The increasing incidence of type 2 diabetes mellitus worldwide poses an immense public health and medical challenge for the implementation of successful preventive and treatment strategies. The concurrent rise in overweight and obesity, which is tightly correlated to type 2 diabetes, interferes with diabetes treatment and increases the likelihood of hypertension, dyslipidemia, and atherosclerosis related diseases.
The pathophysiologic condition preluding the development of type 2 diabetes is related to reduced effects of insulin on peripheral tissues, called insulin resistance. These tissues are mainly muscle, fat and liver. Muscle tissue is the main tissue concerned by insulin resistance in type 2 diabetes. The syndrome characterised by insulin resistance, hypertension, dyslipidemia and a systemic proinflammatory state, is referred to as metabolic syndrome. The prevalence of metabolic syndrome in the adult population in developed countries is 22-39% (Meighs 2003)
Currently the most promising approach to mitigate and deter the metabolic syndrome is lifestyle intervention with weight reduction, decreased consumption of saturated fat, increased physical activity in combination with appropriate pharmacotherapy. Healthy diets that avoid excess energy intake encompass substitution of mono and polyunsaturated fatty acids in exchange for saturated fat. In particular the long-chain omega-3 fatty acids from fatty fish, namely eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) have proven beneficial in prevention of type 2 diabetes.
EPA and DHA have effects on diverse physiological processes impacting normal health and chronic disease, such as the regulation of plasma lipid levels, cardiovascular and immune function, insulin action and neural development and visual function. Firm evidence exist for their beneficial role in the prevention and management of coronary heart disease, dyslipidemias, type 2 diabetes, insulin resistance, and hypertension (Simonopoulos 1999; Geleijnse 2002; Storlien 1998).
Recent studies suggest that omega-3 fatty acids serve as important mediators of gene expression, working via nuclear receptors like the peroxisome proliferator-activated receptors (PPARs) controlling the expression of the genes involved in the lipid and glucose metabolism and adipogenesis (Jump 2002). PPARs are nuclear fatty acid receptors that have been implicated to play an important role in obesity-related metabolic diseases such as hyperlipidemia, insulin resistance, and coronary heart disease.
The three subtypes, α, γ, and δ, have distinct expression pattern and evolved to sense components of different lipoproteins and regulate lipid homeostasis based on the need of a specific tissue. PPARα potentiates fatty acid catabolism in the liver and is the molecular target of the lipid-lowering fibrates. PPARγ on the other hand is essential for adipocyte differentiation and mediates the activity of the insulin-sensitizing thiazolidinedions (the glitazones) through mechanisms not fully understood. (Chih-Hao 2003; Yki-Järvinen 2004) Recently, pharmaceuticals acting as ligands to the PPARγ receptor have been introduced as treatment of type 2 diabetes (Yki-Järvinen 2004). These compounds called thiazolidinediones or glitazones are drugs that reverse insulin resistance which is the pathophysiologic basis for development of the metabolic syndrome and type 2 diabetes. These compounds, of which rosiglitazone and pioglitazone have been launched as pharmaceuticals, lower fasting and postprandial glucose concentrations (which is being manifest as a pathologic glucose tolerance test), plasma insulin as well as free fatty acid concentrations. In this respect the glitazones act as insulin sensitizers.
However, these improvements are generally accompanied by weight gain and an increase in the subcutaneous adipose-tissue mass (Adams 1997). The use of thiazolidinediones is not only associated with weight gain but a subgroup of patients also have fluid retention and plasma volume expansion, leading to peripheral oedema. The increase in body weight and oedema has been associated with an increase in the incidence of heart failure, which is the reason why the Food and Drug Administration has included a warning in the prescription information for rosiglitazone (provided by Avandia) and pioglitazone (provided by Takeda). These adverse effects restrict the use of the glitazones especially in patients with coronary heart conditions. Clearly there is a potential for new drugs with positive effects on insulin resistance but with weight reduction activity and no fluid retention tendency.
The effect of the poly-unsaturated fatty acids (PUFAs) on PPARs are not only a result of fatty acid structure and affinity to the receptor. Factors contributing to the composition of the intracellular non-esterified fatty acids (NEFA) levels are also important. This NEFA pool is affected by the concentration of exogenous fatty acids entering the cell and the amount of endogenous synthesised fatty acids, their removal via incorporation into lipids as well as their oxidation pathways. (Pawar 2003)
Although omega-3 fatty acids are weak agonists of PPARs, when compared with pharmacological agonists like the thioglitazones, these fatty acids have demonstrated improvement in glucose uptake and insulin sensitivity (Storlien 1987). It has been reported that adipocytes were more insulin sensitive and transported more glucose when the polyunsaturated to saturated fatty acid ratio in the diet was increased (Field 1990). Collectively, these data indicate that the 20- and 22-carbon fatty acids, namely EPA and DHA could play a preventive role in the development of insulin resistance.
Due to their limited stability in vivo and their lack of biological specificity, PUFAs have not achieved widespread use as therapeutic agents. Chemical modifications of the n-3 polyunsaturated fatty acids have been performed by several research groups in order to change or increase their metabolic effects.
For example, the hypolipidemic effects of EPA was potentiated by introducing methyl or ethyl in α-or β-position of EPA. (Vaagenes 1999). The compounds also reduced plasma free fatty acid while EPA EE had no effect.
In a recent work published by L. Larsen (Larsen 2005) the authors show that the α-methyl derivatives of EPA and DHA increased the activation of the nuclear receptor PPARα and thereby the expression of L-FABP compared to EPA/DHA. EPA with an ethyl group in the α-position activated PPARα with equal strength as α-methyl EPA. The authors suggest that delayed catabolism of these α-methyl FA may contribute to their increased effects due to decreased β-oxidation in mitochondria leading to peroxisomal oxidation.
Alpha-methyl EPA has been shown to be a stronger inhibitor of platelet aggregation than EPA, both in vitro (Larsen 1998) and in vivo (Willumsen 1998).
Patent Abstract of Japan, publication number 05-00974 discloses DHA substituted in alpha-position with an OH-group, however only as an intermediate. No examination as to possible pharmaceutical effects of this compound is disclosed.
Laxdale Limited has also described the use of alpha substituted derivatives of EPA in the treatment of psychiatric or central nervous disorders (U.S. Pat. No. 6,689,812).

None of these modified fatty acids have, however, shown satisfactory pharmaceutical activity, and none of them has reached the pharmaceutical market.